When climbing multiple pitches of ice you need something like a spring leash, it's just essential safety device that prevents you from loosing your tool in midway. Grivel Double Spring is a good choice for such, it's not particularly fancy, but does its job. It's just about right length and stretchy enough not to affect your movement negatively. Mine has keylock -type of carabiners, whereas newer ones have screwlocks (I think that keylocks are better, easier to operate + lighter)... rotating swivel at the harness attachment point might be handy time to time...

I have the new double springs with screwlocks and have used them with my Grivel Matrix Tech for almost a year now. They are very simple to use, but carabiners are a bit large compared to (for example) BD's spinner leash. However, larger carabiners will probably fit a bit better with any ice axes on the market.

Screwlocks are not the best solution for spring leash because they tend to turn too tight when used. I have spend few times some not_so_quality time with my spring leash to get carabiners open.
Springs seems to be very durable and I have once fell on them (I weight ~95kg) when climbing as second and they didn't seem to get any damage. Still wouldn't use and won't recommend to use them as protection gear.
One little attribute you have to keep an eye on if you tend to switch hands and axes while climbing is that the springs will spin around each other and you have to spin them back once in a while.

I have tried these leashes with Matrix Tech, BD's Vipers and Petzl's Nomics. They worked fine with two first but were terrible with Nomics. This was because the attachment hole for spring in Nomic is in the middle of the grip. Therefore, when you keep axes on your hands, carabiners are also inside your palm and carabiners WILL screw so thight you can't even imagine. The touch with axe is also a bit weird and you can't get as good grip from them as you would like to. I climbed about 40 meters of easy ice with Nomics and used 5 minutes to unscrew the carabiners.

All in all, these are good springs if you are not climbing difficult routes where you don't want to do extra gimmicks with your springs, you do stop in the middle of climbs at times to settle springs and if you don't own Nomics or any other axes with similar spring leash attachment.

I have the older version too, without the screw gates, and I find them quite easy to use. They do sometimes spin around each other and also around the ropes when climbing as a second, but I think It's worth the trouble since you never lose your axe if you fall. I agree about the durability, I've had my whole weight hanging on one half of the Douple spring for several times but they still work perfectly fine. I can warmly recommend these, at least for people who tend to lose grip of their axes:)